This is a 3D printable version of the original "Freebird" easy to build ornithopter. I designed the first one over 30 years ago to make ornithopters easier to build. They used to be a lot more complicated. Over the years, I refined the ornithopter based on experience with school groups and feedback from hobbyists. Thousands of people have made the Freebird, and this simplified design has changed the way ornithopters are made.

This version of the ornithopter uses balsa wood together with 3D printed parts. The balsa wood is much lighter and stiffer than 3D printed plastic. This makes it fly much better than a fully 3D printed ornithopter. At the same time, the 3D printed parts make it easier to build than ever before.

The goal has always been to make something simple but flies good. I decided to post this because I have seen a lot of ornithopters that will not fly. This one does.

Materials:

Balsa wood (available from Hobby Lobby)
. 1/8" square balsa wood sticks (two 8" long)
. 3/32" square balsa wood sticks (two 7" long)
. 1/8x5/16" balsa wood stick (5" long)
0.030" (0.8mm) straight stainless steel wire (ebay)
Good quality tissue paper (plastic film is not recommended)
Rubber earring backers (3, white)
Model airplane rubber 1/8" by 17 inches (faimodelsupply.com)
. Using this high quality rubber is important.
Armor All automotive protectant to lubricate the rubber band

Tools:

You will need needle nose pliers to cut and bend the wire. Smooth off the cut ends with sand paper so they won't cut your fingers when you wind up the rubber band. You will also need a 1/32" drill bit to clear the holes after printing.

Assembly:

1. First get the materials together and print the 3D printable parts.

2. Next bend the wire following the attached PDF instructions.

3. Remove any strings and make sure the 3D printed parts fit together with the balsa wood parts. The front 3D printed part should be glued onto the balsa wood stick with epoxy. The tail pieces don't need glue unless they feel loose. This allows the tail to be removed for storage.

4. The wing hinge wires can be secured onto the wing spars by wrapping with tissue paper coated with a thin layer of white glue (Elmer's Glue All). Or you can use heat shrink tubing (put in place after making the first bend in the wire). It is OK for the wing spar to swivel around the wire.

5. The wing tissue should not be too floppy, and it must be equal on the two sides. The tissue paper holds the wing hinge wires in place, so they must be all the way in their holes when you glue the tissue to the top of the body.

6. Make sure the connecting rods are not switched. The wings should move symmetrically when you turn the crank.

7. Cut a strip of rubber 17 inches long. Tie the ends together as shown in the PDF. Lubricate with Armor All. Double the rubber band and hook it onto the ornithopter. Wind up 50 turns for a test flight or 200 turns after making adjustments.

Flying:

Adjustments may be required before the ornithopter will fly.

To adjust for flight, wind up the rubber band 50 turns. Toss the ornithopter very gently with a horizontal motion but a slight upward angle. Don't throw it hard. Let the wings do the work. At 50 turns it should descend slowly and fly almost straight.

If the ornithopter turns sharply to one side, add a little weight to the wingtip on the outside of the turn. You can carefully insert a small straightpin into the end of the wingspar, or put tape there. Adjust the weight until the ornithopter flies in a large circle or almost straight. It will never fly perfectly straight because there is no rudder.

Here are the instructions for the non-3D printed original Freebird ornithopter:
https://ornithopter.org/archive/freebird.pdf